These studies are designed to examine the effects of hormones and other factors on the synthesis and metabolism of brain monoamine neurotransmitters, and the participation of these monoamines (the catecholamines dopamine, norepinephrine, and epinephrine; the indoleamine serotonin) in the control of secretion from the pituitary gland. They include the following research programs: 1) Effects of alterations in plasma concentrations of thyroid, pituitary, or gonadal hormones on brain catecholamine synthesis; 2) Effects of hormonal peptides and their behaviorally-active analogues on brain monoamine metabolism; 3) The mechanisms by which drugs acting on central monoaminergic synapses modify the secretion of prolactin and other pituitary hormones; 4) The relation between the peripheral metabolism of tyrosine and the synthesis of brain catecholamines; 5) the effects of diet-induced changes in brain monoamine synthesis and the secretion of hormones from the anterior and posterior pituitary glands (vasopressin; growth hormone); and, 6) The mechanisms and consequences of the changes in brain monoamine levels resulting from alterations in cerebral blood flow.